It's trouble again in paradise for Meredith and Derek in the fourth episode of 'Grey's Anatomy' season 11 called 'Only Mama Knows.' According to spoiler reports, the fight will be ignited by Meredith's relationship with her mother, Ellis, who passed away.

The last episode showed how Meridith discovered some unwanted truths in her life by rummaging through hospital records

It is said that Derek and Meredith's misunderstanding will also be about Derek finally confronting Meredith about his job in Washington.

The two have been setting the issue aside and Derek feels that it is time to talk about it. After arguing, Derek makes a comment about Meredith being like her mother, which will anger her for obvious reasons.

Having a not-so-pleasant conversation with Maggie, Meredith finds out that she is indeed her half-sister, along with some events in the past concerning their mother.

The upcoming episode, to be premiere on October 16, will show how Meredith gets a hold of old photos and videos showing her mother, Ellis. Meredith will also read journals of her mom, which will lead to discoveries that she might not be prepared for.

Aside from Meredith finding out the truth about her mother, Maggie will also come to terms with some unexpected hurdles. Maggie will make a startling announcement at the Grey Sloan Memorial Hospital which will leave everyone in absolute shock.